Renal (Kidney) Amyloidosis in Dogs

Renal amyloidosis (RA) in dogs is a rare kidney condition.  This condition results in abnormal deposits of proteins that come from the metabolism of protein into the kidneys.  While the cause of the amyloidosis is unknown, the amyloid deposits can be found virtually anywhere and in any type of tissue in the body.  It is an inherited trait for some breeds (Chinese Shar Peis) but has also been found in Beagles, Collies, and Walker Hounds.  While these breeds have an increased risk, German Shepherds and mixed-breed dogs seem to have a decreased risk.  

This disease tends to be diagnosed in older dogs, the age of 9 years old being the average age except in Shar-Peis whose average age at death is 4 years old, and it can occur at younger ages in any breed.  It is felt that chronic infections and inflammatory conditions could be a factor in the development of renal amyloidosis in dogs.

The term renal refers to the kidneys, and amyloidosis is defined as a rare as well as serious disease caused by the accumulation of proteins in the form of abnormal insoluble fibers.  This accumulation is progressive and can be fatal in certain vital organs.

Here are the symptoms to watch for in your pet.  Call your veterinary professional as soon as possible if these are noted:

• Unusual thirst
• Frequent urination
• Loss of appetite
• Weight loss
• Vomiting
• Breathing that may be labored
• Fluid retention
• Swelling of limbs and face
• History of joint swelling and fever, especially in your Shar-Pei

Types

The type of amyloidosis is dependent upon the organ or tissue in which the amyloids are found, which can be in any organ and in any type of tissue in the body.

• Kidney - results in protein loss in urine and eventually to chronic kidney failure
• Liver, spleen, pancreas - these deposits will cause malfunction of these organs as well

Amyloids can be in any type of tissue or organ and if it disrupts the function of the kidneys, liver or heart, the disease could be fatal.

Amyloids result from errors in protein folding (a metabolic process in which a protein is eventually enabled to perform their biological function).  This insoluble protein gets deposited into the kidneys or in other organs/tissues in the body and then these proteins interrupt the biological function of the organ/tissue into which it is deposited.  

• Abnormal amyloid deposits into the kidneys cause loss of protein in the urine 
• Some specific diseases have been noted in some dogs though not necessarily considered the cause of renal amyloidosis (fungal diseases, chronic bacterial infections, heartworm diseases and cancer)
• The inherited form strikes earlier in life than non-inherited form
• Both sexes are affected but slightly higher risks exist for females

Your veterinarian will need to do some blood and urine testing as well as x-rays to confirm the diagnosis of renal amyloidosis.  

Blood Tests 

A complete blood and chemistry panel won’t necessarily diagnose amyloidosis but these tests will likely show elevations of some of the proteins that are normally lost.  The complete blood panel will also give insight into the function of other systems of the body such as anemia, cholesterol as well as kidney markers and low protein levels and albumin levels.

Urinalysis 

This will reveal excessive protein. This is a significant marker for kidney amyloidosis but additional tests in this area will be needed to determine the degree of protein loss. Urine protein and creatinine ratio confirms degree at which the protein is being lost in the urine.

X-rays

This test isn’t as revealing as you might think because the size of the kidney that will be visible on the x-ray isn’t always definitive of renal amyloidosis.  The kidney size can be smaller than normal or larger than normal and thus the test results are not as informative as other tests.

Additionally, biopsy of the kidney may be required to provide the absolute diagnosis of amyloidosis versus other kidney or renal disorders which can also result in excessive protein loss in the urine. One of the most important aspects of the protein loss is the fact that one of the proteins in question is responsible for prevention of the formation of blood clots.  Thus, excessive loss of this protein can lead to increased risks of blood clots in the lungs which cause the symptom of labored breathing.  Excessive loss of the protein albumin can lead to an accumulation of fluid in the abdomen (ascites) as well as edema or swelling of limbs and face, though ascites and edema are fairly uncommon in dogs diagnosed with renal amyloidosis.

Unfortunately, the treatment of renal amyloidosis in dogs may be difficult and frequently unsuccessful.  This is especially the case if the kidney failure has already begun.  These are the steps your veterinary professional will likely be initiating:

• After identification of the root cause of the infectious or chronic inflammatory condition that may have caused the amyloidosis to develop, treatment will need to be initiated
• If there is kidney failure already found, management of that condition will be needed; this may mean hospitalization, IV fluids or perhaps only outpatient care, other steps might include prescription diets, hormonal supplements or dietary supplements
• Most dogs present in later stages of renal amyloidosis, but in those cases in which the animal presents in very early stages, experimental therapy such as DMSO (dimethyl sulfoxide) administration has been an effective treatment
• Colchicine, which has been shown to be of benefit for humans under certain circumstances has yet to be studied in dogs

For the best results of any treatment of your dog for renal amyloidosis, a mix of home as well as professional veterinary care will be needed.  As with any disease or condition, your dog will require essential follow up care and keeping up with the required follow up is critical to the care of your pet, especially in those cases in which the dog is slow to improve.  Be sure to administer all medications as your veterinarian has directed and let them know if you experience problems.  

Be diligent to feed your dog the low protein prescription diets as recommended by your veterinary professional.  Be sure to keep up with those follow up appointments with your veterinary caregiver as she will be interested in performing serial urine protein and creatinine ratios to follow the response of the protein loss to the treatment.  Additionally, your veterinarian will likely want to do serial chemistry panels to compare the results to monitor the success or failure of therapy.